Tag Archives: led

I always wanted one of those colourful glowing large TV screens in my living room but I never felt like paying a fortune for it. So, why don’t do it on my own? I ordered two Raspberry Pis, which seemed like a perfect fit for a media center and a LED controller because of the built in SPI bus interface. After some research, I decided that using SMD LED strips with WS2801 chips would be the best match for a Raspberry Pi controller. Furthermore SMD strips are quite easy to mount, because of the adhesive tape on the back of the strip.

Demonstration

Hardware installation

We’ll setup the necessary hardware first.

Parts list

I’ve ordered following parts to complete the installation from boxtec.ch

1 x

5V LED Pixel Strip 5m (WS2801)

1 x

AC adapter 5V/10A

4 x

RGB LED Strip – Pigtail Connector 20cm (pair)

1 x

Heat Shrink Kit

1 x

Breadboard Jumper Wire m-m (65-cable pack)

1 x

1pin dual female jumper wire (300mm) 20pcs.

1 x

5.5 x 2.1mm DC Power Jack Adapter (f)

1 x

2pin dual female jumper wire (300mm) 5pcs.

2 x

Raspberry Pi Model B

2 x

8GB SD memory cards

1 x

1A MicroUSB AC adapter

You’ll also need tools for soldering. Alternatively, you could use just one Raspberry Pi, which will act as the LED controller and the media center.

LED power consumption

Regarding the spec sheet, the 5 V LED strip consumes approx. 7.68 Watts per meter or 1.5 A. To calculate the total power consumption, we need to measure how many LEDs we can put on the TV’s back. I needed 3.8 m of the SMD LED strip for my 55 inch TV.

Power supply calculation

Fortunately, the Raspberry Pi requires also 5V, so you’ll be able to power up the strip and the Pi with the same 5V power supply. Just don’t forget to order a DC Power Jack Adapter for easy connectivity of the at least 7 A / 35 W – 5V power supply.

LED strip soldering

As a Software Developer, I’m not an expert in soldering but I tried to do my best. Cut the strip into 4 pieces that match your TV dimension. For easy replacing of a broken LED strip or moving the installation to another TV connect the stripes with pigtail connectors.

WS2801 LED strips have always four connectors. In my case with those pinouts:

5V

GND

SD

CLK

Be careful, don’t twist those between the pigtails! There’s also an arrow on the strip, which marks input / output. Make sure you’re able to connect the strips from input to output with the pigtail connectors.

It’s easier to solder the connectors to the fine SMD if you put some soldering to each of the four joints in advance. Finish it up with a heat shrink, for more flexibility use non-adhesive heat shrink tubes.

LED mounting

Now, we’re coming to the fun part. It’s barely easy to mount the strips because we chose SMDs, just use the adhesive tape and you’ll be fine. It’s essential that you start mounting from the bottom right, seen from the back of the TV with the arrow on the strip pointing to the right. Later, you’ll connect from the GPIO from the RPI directly to this input of the strip. Then go ahead counter clockwise, connecting the output of the first strip to the input of the second strip and so on until you reach the bottom left. The output of the last strip is left empty, so the strips are not connected in a loop.

LED strip wiring

Wire the LED’s up as shown in the following diagram created by Philip Burgess. Please note, the diagram shown, is for the Rpi revision 1.0. This could slightly change with later revisions. Make sure the input +5V/GND connectors of the strip and the Raspberry Pi power connectors are directly connected to the DC Power Jack Adapter (DC Jack).

There’s no need for the Pi’s micro USB port anymore. I’d suggest using Breadboard Jumper wires for proper connections to the Pi’s breakout board. Leave the output connectors of the LED strip as they are.

Prototyping: All wires connected to the Raspberry Pi.

Final outcome: Raspberry Pi in black enclosure and power supply wired up.

Software installation

So, the hardware is prepared. In this section I’ll show you how to setup two different applications on the Raspberry Pi to control the LEDs. You have to chose one of them, I’d recommend Hyperion for various reasons.

Hyperion

Hyperion is newer, features a JSON interface and is easier to setup than Boblight. It is also less resource hungry. Therefore we can easily run XBMC and hyperion on the same Raspberry without performance issues.

Install a media center distribution for the Pi. I recommend Raspbmc for beginners, it’s easier to install and less locked down.

Boot up Raspbmc and remote login with your host computer. You’ll find the IP in XBMC under Settings -> System Info. If you’re on Windows, use putty for the ssh connection.

Now we create the hyperion config file which includes for example the LED position informations. It’s a very readable JSON format. The configuration can initially be generated by a Java tool called “HyperCon”. Have a look at the instructions page. Download HyperCon to your Host computer where Java must be installed. If you followed the LED installation instructions above, the following settings should give you reasonable results for a start. Please adjust the LED counts and the 1st LED offset for your setup on the “Hardware” tab. We want the LED offset to line up with the LED closest to the initial input, which is connected to the Rpi GPIO. Then click “Create Hyperion Configuration” and save the json file to your Desktop. Don’t rename the file.

Let’s copy “hyperion.config.json” to the “pi” user home directory on the Raspbmc. You can easily copy the file by using the shared folder “raspbmc”. Make sure you put it in the folder pi/hyperion. Alternatively you could use SCP for copying the file.

Back on the Raspbmc ssh shell, copy the configuration file to the place where it will actually be picked up by hyperion at boot.

We’re nearly finished. Hyperion grabs the color information directly from XBMC over an interface running on port 9090. We configured this in HyperCon, tab “External”. By default, this remote interface is disabled. In XBMC goto Settings -> Services -> Remote Control and activate both options. Reboot the system.

We’re finished, play a movie or display some pictures and the LEDs should light up. The LED are disabled in the menu, you could easily change this setting in /etc/hyperion.config.json, look for “xbmcVideoChecker”.

If you’d like to use the LED as mood lights simply install following excellent app and point it to the Raspberry Pi with port 19444: Hyperion for Android. For non Android users, there’s also a web app available.

Boblight

I’d recommend using ArchLinux as distribution for the Raspberry Pi, it boots in less than 10s to the command line.

Now generate the boblight config file. Switch to the boblight checkout directory create on step 3 and make the config script executable.

Shell

1

chmod+xmakeconfig.sh

Then execute the script

Shell

1

./makeconfig.sh

The script will ask you for the exact LED count mounted on each side of your TV. Use the default values for all other inputs. Wait till the script is ready, then copy everything between “——- Light section starts here ——” and “——- Light section ends here ——” into a text file on your host machine (Not on your Pi). Write down the total LED count.

Download this preconfigured config file: SPI-WS2801-basic and open it with a texteditor on your host machine. Add your generated light section simply to the end of the file. Multiply your total LED count by 3 (RGB channels) and replace “369” with your result in the file. Then select all and copy.

Create the actual boblight config file with

Shell

1

nano/etc/boblight.conf

on your Pi and paste the content of your modified config file on the host machine into it, this will take some time to complete.

boblight-dispmanx installation

So, we’ve managed getting boblight to control our LEDs. Now, we’ll see how to setup another tool for sending captured screen color information right to our boblight deamon, it’s called boblight-rpi. Perform the following steps on the Raspberry Pi, that will be running the media center. A media center for example XBMC, running on this Pi will act as the video input source. Everything played on XBMC will be captured by boblight-dispmanx and sent to boblight.

Don’t forget to replace the {placeholder} with the IP of your boblight running Pi or set it to “localhost” if you went for one Raspberry Pi. Then save the script and make it executable with

Shell

1

chmod+x/storage/.config/autostart.sh

We’re done, just restart the system

Shell

1

sudo reboot

Check the setup with a RGB test video. If you think the colours are to pale, try a higher value for the “-o saturation” parameter. When the lights are to slow, try setting “-o speed” to 90. If you don’t like the LED’s in the XBMC menu, just remove the “-b” parameter.

Conclusion

This is a really educational project, which will give insight into a lot of interesting technical areas reaching from compiling in the Linux shell to soldering and calculating LEDs power consumption.